Document US-A-6 108 200 describes an example of such apparatus, in which the portable electronic appliance is a digital personal assistance (PDA) provided with a special communications interface suitable for connection to a complementary interface of a keyboard.
Nevertheless, that solution is expensive insofar as it implies providing the portable electronic appliance with an additional communications interface. The extra cost is a drawback whatever the kind of portable electronic appliance under consideration, and it becomes completely unacceptable when the portable electronic appliance is an appliance produced with a very small profit margin, as is the case for radiotelephones for private radiocommunications networks (for example of the digital European cordless telecommunications (DECT) type, of the Bluetooth type, or of some other type).